The continuing overall objective of this research project is to determine the rates of production and utilization of selected blood-borne metabolites in normal, fasting and diseased man by means of isotope tracer techniques. Glucose, free fatty acids and the ketone bodies are the principal metabolites of interest because of their major contribution as fuels for caloric homeostasis. Their metabolism is of particular interest during starvation because at this time physiological and biochemical mechanisms operate maximally to conserve essential body constituents. Currently our major research efforts are devoted to comparative studies of ketone body metabolism during starvation induced ketosis and diabetic ketosis with special emphasis on acetone metabolism.